Drop As You Move ...

With Pherophone, you can leave and detect
digital pheromone drops at the touch of a button.
Using the app on your mobile smartphone, you can drop messages as
you move around, creating virtual, temporary
signposts. Notify others of a garage sale, hot spot for food, traffic detour,
the possibilities are endless. Currently, the user can set the messages to dissipate
from 10 minutes to 6 hours,
and to have a range of 100 - 4000 meters (about 328 feet to 2.5 miles.

And Sniff Where You Are!

Anyone can detect your pherophone drops through sniffing at a location.
The sniff will detect the direction of the drop, shown with a compass
direction (N, E, S, W), and the intensity of the drop, a number between 0 and 1. Drops
begin at an intensity of 1, and as a
drop dissipates, the intensity will fall. The drop will expand linearly,
until the central intensity reaches 0 and the drop fades away.